The present invention relates generally to electropneumatic ("EP") brake control valves and more specifically, to a retrofoot unit to convert a pneumatic brake control valve to electropneumatic brake control valve.
Electropneumatic brake control valves are well known in the passenger railroad art and the mass transit railroad art. Because the trains are short and are not involved generally in a mix and match at an interchange of different equipment, the ability to provide pneumatic and electrical control throughout the train has been readily available in the passenger and the mass transit systems. In freight trains, the trains may involve as much as 100 cars stretching over one mile or more. The individual cars may lay idle in harsh environments for up to a year without use. Also, because of the long distance they travel, the cars are continuously moved from one consist to another as it travels to its destination. Thus, the use of electropneumatic-pneumatic valves in the freight trains has been very limited.
A typical example of electropneumatic control on individual cars of a passenger train is U.S. Pat. No. 2,897,011 to Cotter. A magnetic application valve and release valve are connected with the brake pipe and a control reservoir to locally produce a pneumatic signal simulating a brake pipe signal to control the individual pneumatic control valve at each of the cars.
The major use of electropneumatic valves in freight trains have been at the locomotive. This is where electric power is available and the electrical interconnection is easy to achieve. Also, by the use of radio waves, the simultaneous braking at various positions along the train using slave locomotives with electro-pneumatic valves has also been used on freight trains. Recently, the American Association of Railroads ("AAR") has undertaken a massive study to determine an appropriate regime of incorporating electropneumatic valves on each of the cars of a freight train.
Various overlay systems have been proposed for use with control valves for freight trains. One is shown by U.S. Pat. No. 5,390,988 to Shank. This is an overlay system wherein an adapter is inserted to the service portion of a standard pneumatic brake control valve and electrically operates pneumatic valves to pneumatically control a standard brake control valve. The overlay is inserted between the service portion and its accelerated release valve portion. It is a pilot adaptor wherein the electropneumatic portion provides pneumatic signals to the control valve to operate in its normal matter. The only direct connection of the electropneumatic portion and the brake cylinder is for graduated release wherein the brake cylinder can be connected to exhaust through the electropneumatic valve.
Another overlay system is illustrated in U.S. Pat. No. 5,335,974 to Klink. This system also includes an electronic module and electropneumatic valves connected to a standard freight control valve. A pneumatic interface with transducers is provided between the service portion and the pipe bracket of a standard pneumatic brake control valve.
Another recent overlay system for a freight brake control valve is shown in U.S. Pat. No. 5,393,129 to Troiani et al. The two previously discussed patents to Shank and Klink provided adaptors or overlay to the service portion of the control valve or at the interface between the service portion and the pipe bracket so as not to change the connection of the train fluid system to the pipe bracket. Troiani et al. provides their overlay at the connection of the pneumatic system to the pipe bracket. The electropneumatic valve system is connected to the emergency reservoir and between the retainer port of the pipe bracket and the retainer.
A train inspection apparatus is disclosed in U.S. Pat. No. 2,993,199 to Browne et al. A pneumatic interface is provided between the emergency portion and the pipe bracket. This interface not only monitors the condition of the brake valve but also allows electropneumatic operation or an overlay of the pneumatic operation of the pneumatic brake valve. As with Shank and Klink, Brown et al. does not require modification of the connection of the fluid systems to the pipe bracket.
It is an object of the present invention to provide an electropneumatic retrofit unit which can be mated with either the emergency or service portion pipe bracket interface.
It is another object of the present invention to provide an electromagnetic retrofit unit for a pneumatic brake control valve which can operate as an overlay with a complete brake control valve or in combination with either the emergency or service portion, or as a complete stand alone.
An even further object of the present invention is to provide an electropneumatic unit for installation on new cars that is designed for electropneumatic operation only.
These and other objects are achieved by an electropneumatic unit for a pneumatic brake control valve connectable to an interface of the emergency brake portion or service brake portion of a standard pipe bracket as a retrofit or by itself. The unit includes an EP interface having an EP brake pipe port, EP brake cylinder port and an EP emergency reservoir port for interfacing with the corresponding ports at the brake pipe interface. An electrical control valve, which is connected to the EP emergency reservoir port, has a venting port and an output port. The electrical control valve selectively connects its output port to the venting port for releasing a brake or connects the EP emergency reservoir port to its output for applying the brake. A pneumatic brake cylinder valve is responsive to the output of the electrical control valve for selectively connecting the EP brake cylinder port with the EP emergency reservoir port or a venting port.
An isolation valve is connected to the brake cylinder valve for preventing the output of the electric control valve from inadvertently operating the brake cylinder valve. The isolation valve may be an electrically controlled valve or a pneumatically controlled valve. The isolation valve may connect the output of the electrical control valve to a venting port to thereby prevent the brake cylinder valve from connecting the EP brake cylinder port with the EP emergency reservoir port. The isolation valve may be responsive to a braking signal from the pipe bracket at an EP brake signal port or the brake pipe pressure, such that the pneumatic brake cylinder valve is responsive to the electrical control valve when there is either no brake signal at the EP brake signal port or the brake pipe is not being modulated for pneumatic braking. The isolation valve may also connect the EP brake signal port to the EP brake cylinder port when preventing the output of the electric control valve from operating the brake cylinder valve.
As an alternative, the isolation valve may also connect the EP brake signal port to the brake cylinder valve to operate the brake cylinder valve when preventing the output port of the electric control valve from operating the brake cylinder valve. As a further alternative, the unit could include a pneumatic selection valve to selectively connect the EP brake cylinder port either with the EP brake signal port or the output of the brake cylinder valve. The selection valve may select the higher of the two signals.
The control unit may also include a pneumatic emergency valve separate from the isolation valve for selectively connecting the EP emergency reservoir port to the brake cylinder valve in response to an emergency signal in the EP brake pipe port. The pneumatic emergency valve is responsive to brake pipe recharging to cause the brake cylinder valve to release the brakes. The emergency valve and the selection valve may be combined such that the emergency valve also disconnects the output port of the electric control valve from the brake cylinder valve in response to an emergency signal.
The unit may also include a charging choke and check valve which allows the EP brake pipe port to charge an emergency reservoirs and/or an auxiliary reservoir connected to EP emergency reservoirs port and EP auxiliary reservoir ports through the unit. The unit may be connected directly to and replace the service portion at the service portion interface to the pipe bracket or may be connected through an adaptor plate to the emergency portion interface to the pipe bracket. When the unit is connected to the service portion, the emergency portion may be connected to the pipe bracket and used as a vent valve. The emergency portion may be replaced with a vent valve. Alternatively, the emergency portion may also be removed and covered by a blank plate. The unit includes one or more transducers for sensing pressure in one of the EP ports and electronics on the unit for operating the electrical control valve and any other electrical valves in the unit.
The electropneumatic control unit may also be a separate stand alone unit in combination with an electropneumatic brake system independent of a pneumatic brake valve. In addition to the interface and the electrical control valve, it would include a pneumatic brake cylinder valve responsive to the output port of the electrical control valve for selectively connecting the EP brake cylinder port with the EP reservoir port or a venting port. This unit can also include a pneumatic emergency valve for selectively connecting the EP reservoir port to the brake cylinder valve in response to an emergency signal in the EP brake pipe port. As in the other embodiment, the emergency valve may also disconnect the output port of the electrical control valve from the brake cylinder valve in response to an emergency signal in the EP brake pipe port.
The unit may also include a release interface having a first and second brake cylinder port connected respectively to the EP brake cylinder port and to the brake cylinder valve or the selection valve for mating with respective ports on a manual release valve to be mounted at the release interface. Thus, the manual release valve can release the brakes without draining reservoir pressure. The release interface also includes a reservoir port interface so as so allow the manual release valve to also discharge the reservoirs.
In another embodiment, the electropneumatic control unit would include the EP interface and the electrical control valve in combination with the pneumatic isolation valve. The pneumatic isolation valve is responsive to pressure in the EP brake pipe port for selectively connecting the EP brake signal port and the EP brake cylinder port when the EP brake pipe pressure signals a brake application. The pneumatic isolation valve also connects the output of the electrical control valve to the EP brake cylinder port when the EP brake pipe pressure signals the brake release. Alternatively, the pneumatic isolation valve may be responsive to pressure in the EP brake signal port and at the output port of the electrical control valve for selectively interconnecting the EP brake signal port and the EP brake cylinder port when the EP brake signal port pressure signals and brake application. The pneumatic isolation valve connects the EP emergency reservoir port to the EP brake cylinder port when the EP brake signal ports pressure signals a brake release and the output port of the electrical control valve signals a brake application.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.